This sounds...interesting, but I don't know if I fully understand your request. It may not be as simple as having a playback speed, and a "speed" at which the randomizer jumps to a new frame.
It sounds like this would require an additional variable –– a number of frames to play (in forward order) before skipping to a new random frame. Resolume would jump to a random frame, plays some number of frames in forward order, skip to another random frame, play the number of frames in order again, and so on. (e.g. setting this new variable to 30 frames would play one second of the clip before jumping to a new random frame.) Resolume would essentially have to "switch" back and forth between random and forward playback modes. You could then set the (forward) playback speed of the original clip to whatever you would want.
It would be much easier for the VJ to drop in multiple copies of their video into the same Layer, and divide the video up into smaller bits, with each "bit" getting its own clip. Then, you select all bits, and set their Auto Pilot to "Play Random Clip." If the entire Layer is one video file broken up, you will get the same visual effect as Random playback, only you can then control how much of the clip is played at a time, and the playback speed of each individual bit. I know this turns a Clip into a Layer, but it's much faster and more effective than hoping for software updates.
IMO, if we're talking new play modes, the one where a video loops with a crossfade between it's own ending/beginning takes priority. The one major benefit you mention is that if you could set a "duration" for the video to play before jumping to a random frame, you could in theory MIDI Map the "jump rate" to 1/4 Bar, 1 Bar, etc.
Hope this helps!